Illinois ABP Shading Study Requirements
Illinois ABP Shading Study Requirements

Illinois ABP Shading Study Requirements

The following is taken from page 27-28 of the Adjustable Block Program’s Final Guidebook:

Shading Study

A shading study shall be completed for all projects. Suitable shading studies can include, but are not limited to, using tools such as the Solar Pathfinder, Steprobotics, Helioscope, and HORIcatcher as well as or in conjunction with software designed to perform shading analysis. The Program Administrator and IPA reserve the right to request further information on any shading study or the system used to obtain that shading study. Applicants can request approval of a given shading study software or system prior to application, however applicants are not required to obtain pre-approval for the use of shading study software.


In order to use the standard capacity factor, a system must meet the Minimal Shading Criteria.

The Minimal Shading Criteria is:

No obstruction is closer than a distance (“D”) of twice the height (“H”) it extends above the PV array. All obstructions that project above the point on the array that is closest to the obstruction shall meet this criterion for the array to be considered minimally shaded. Any obstruction located north of all points on the array need not be considered as shading obstructions. Obstructions that are subject to these criteria include:

1. Any vent, chimney, architectural feature, mechanical equipment, or other obstruction that is on the roof or any other part of the building.

2. Any part of the neighboring terrain.

3. Any tree that is mature at the time of installation of the PV system. 4. Any tree that is planted on the building lot or neighboring lots or planned to be planted as part of landscaping for the building. (The expected shading shall be based on the mature height of the tree.)

5. Any existing neighboring building or structure.

6. Any planned neighboring building or structure that is known to the applicant or building owner.

7. Any telephone or other utility pole that is closer than 30 feet from the nearest point of the array.

Also Required for Use of Standard Capacity Factor:

Any arrays (i) with an azimuth greater than 270 or less than 090, (ii) with a tilt of greater than 80 degrees, or (iii) that do not meet the Minimal Shading Criteria may not use the standard capacity factors and must either use an alternative capacity factor.